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Synlett 2010(13): 1963-1965  
DOI: 10.1055/s-0030-1258488
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Regioselective Synthesis of 5-Chlorosalicylates by One-Pot Cyclization of 1,3-Bis(trimethylsilyloxy)buta-1,3-dienes with 2-Chloro-3-ethoxy-2-alken-1-ones

Olumide Fatunsina, Mohanad Shkoora, Sergé-Mithérand Tengho Toguema, Abdolmajid Riahia, Olapeju O. Aiyelaagbec, Emmanuel T. Akintayod, Christine Fischerb, Peter Langer*a,b
a Institut für Chemie, Universität Rostock, Albert Einstein Str. 3a, 18059 Rostock, Germany
Fax: +49(381)4986412; e-Mail: peter.langer@uni-rostock.de;
b Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert Einstein Str. 29a, 18059 Rostock, Germany
c Department of Chemistry, University of Ibadan, Ibadan 200284, Nigeria
d Department of Chemistry, University of Ado-Ekiti, P.M.B 5363, Ado-Ekiti, Nigeria
Further Information

Publication History

Received 11 March 2010
Publication Date:
09 July 2010 (online)

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Abstract

A variety of 5-chlorosalicylates were prepared by regio­selective one-pot cyclizations of 1,3-bis(trimethylsilyloxy)buta-1,3-dienes with novel 2-chloro-3-ethoxy-2-alken-1-ones.

Key words

organochlorine compounds - cyclizations - silyl enol ethers - arenes

    References and Notes

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11

General Procedure for the Synthesis of 2a-f
To a solution of 1a-f (1 equiv) in Ac2O (3 equiv) was added triethyl orthoformate (3 equiv). The mixture was heated for 15 h at 140 ˚C. The mixture was dried in vacuo and was purified by chromatography (silica gel, heptanes-EtOAc) to give 2a-f.

12

2-Chloro-3-ethoxy-1-phenylprop-2-en-1-one (2a) A mixture of 1a (2.00 g, 12.9 mmol), triethyl orthoformate (6.5 mL, 38.8 mmol) and Ac2O (3.7 mL, 38.8 mmol), was refluxed for 15 h at 140 ˚C, and the resultant mixture was purified by chromatography (silica gel, n-heptane-EtOAc) to give 2a as a brownish oil (2.10 g, 76%). ¹H NMR (300 MHz, CDCl3): δ = 1.32 (t, ³ J = 7.1 Hz, 3 H, OCH2CH 3), 4.10 (q, ³ J = 7.1 Hz, 2 H, OCH 2CH3), 7.37-7.44 (m, 4 H, CH, CHAr), 7.52-7.55 (m, 2 H, CHAr). ¹³C NMR (75 MHz, CDCl3): δ = 15.3 (CH3), 66.0 (OCH2), 113.8 (CCl), 128.7 (2 × CHAr), 128.8 (2 × CHAr), 134.0 (CHAr), 138.2 (CAr), 160.5 (CH), 189.5 (CO). IR (neat): 3368 (w), 3062 (w), 2980 (w), 2935 (w), 1747 (m), 1691 (s), 1596 (m), 1449 (m), 1372 (m), 1216 (s), 1181 (m), 1085 (m), 1000 (m), 965 (m), 846 (m), 754 (m), 686 (s), 640 (m), 600 (m), 561 (m) cm-¹. Anal. Calcd for C11H11O2Cl: C, 62.66; H, 5.22. Found: C, 62.85; H, 5.03.

13

General Procedure for the Synthesis of 4a-q To a CH2Cl2 solution (2 mL/1.0 mmol of 2a-f) of 2a-f was added 3a-d (1.1 mmol) and, subsequently, TiCl4 (1.1 mmol) at -78 ˚C. The temperature of the solution was allowed to warm to 20 ˚C over 12 h with stirring. HCl (10%, 20 mL) was added to the solution, and the organic and the aqueous layers were separated. The latter was extracted with CH2Cl2 (3 × 20 mL). The combined organic layers were dried (Na2SO4), filtered, and the filtrate was concentrated in vacuo. The residue was purified by chromatography (silica gel, heptanes-EtOAc) to give 4a-q.

14

Methyl 6-Chloro-3-hydroxybiphenyl-2-carboxylate (4a) Starting with 2a (316 mg, 1.5 mmol) and 3a (430 mg, 1.65 mmol), 4a was isolated after chromatography (silica gel, n-heptane-EtOAc) as a yellowish oil (177 mg, 45%). ¹H NMR (300 MHz, CDCl3): δ = 3.32 (s, 3 H, OCH3), 6.92 (d, ³ J = 8.9 Hz, 1 H, CHAr), 7.05-7.08 (m, 2 H, CHAr), 7.27-7.35 (m, 3 H, CHAr), 7.42 (d, ³ J = 8.9 Hz, 1 H, CHAr), 10.65 (s, 1 H, OH). ¹³C NMR (75 MHz, CDCl3): δ = 51.0 (OCH3), 113.1 (CCOOCH3), 117.4 (CHAr), 124.0 (CCl), 126.2 (CHAr), 126.6 (2 × CHAr), 127.5 (2 × CHAr), 134.1 (CHAr), 138.7, 140.8 (CAr), 159.2 (COH), 169.6 (CO). IR (neat): 3058 (w), 3025 (w), 2951 (w), 2925 (w), 2852 (w), 1739 (w), 1666 (s), 1593 (m), 1499 (w), 1435 (s), 1334 (m), 1289 (m), 1206 (s), 1135 (m), 1093 (m), 1027 (w), 1000 (w), 963 (m), 825 (m), 770 (m), 748 (s), 698 (s), 690 (s), 635 (m), 610 (m), 573 (m) cm-¹. GC-MS (EI, 70 eV): m/z (%) = 262 (³5Cl, 68) [M]+, 230 (100), 202 (63), 168 (11), 139 (81), 113 (6), 87 (7), 69 (8). HRMS (EI): m/z calcd for C14H11O3 ³5Cl [M]+: 262.03912; found: 262.03916.